UV radiation with mercury UV lamps is widely used for disinfecting and oxidation of contaminants in the liquids. However, mercury UV lamps have a long warm-up period (at least a few minutes), which increases the startup time of operation, and the lamps cannot be operated in a pulsed mode. Mercury UV lamps cannot be turned on immediately after the shutdown, making it difficult to continue their operation after an unscheduled shutdown. There are major problems with their disposal; they are not environmentally friendly, it is necessary to control the mercury vapor level, the lamps must be transported in special containers, and mercury cleaning in the event of damaged lamps is an additional expense. In addition, during irradiation of pathogens by a mercury UV lamp, a content of remaining living organisms is relatively high due to their photo-reactivation, i.e. there is incomplete breakdown of the structure of DNA of the microorganisms from a single exposure of the spectral emission line of mercury.
UV lamps have been used to generate ozone. The creation of ozone requires the use of a lamp, which is designed to allow 185 nm to transmit through the lamp sleeve. Air (usually ambient) is passed over an UV lamp, which splits oxygen molecules (O2) in the gas. The resulting oxygen atoms O−), seeking stability, attach to other oxygen molecules, forming ozone (O3). The ozone is injected into contaminated liquid or air stream, where it inactivates contaminants. However, the maximum ozone production rate is very low; namely, maximum concentration of ozone that can be produced by 185-nm UV lamp is 0.2 percent by weight, approximately 10% of the average concentration available by corona-discharge. Considerable more electrical energy is required to produce a given quantity of ozone by UV radiation than by corona-discharge. Lower gas phase concentrations of ozone generated by UV radiation translate into the handling of much higher gas volumes than with corona-discharge generated ozone.
The technologies involved in corona-discharge ozone generators are varied, but all operate fundamentally by passing oxygen-containing gas through an electrical field. The electrical current causes the “split” on the oxygen molecules as described above on UV ozone generation. For production of ozone, corona-discharge is used more because of the greater advantages of this method. Advantages are the relatively lower costs for ozone production (more cost-effective compering with UV ozone generation) and the greater durability of the system. However, the existing barrier discharge ozone generators are expensive; they require a large area for their installation, and they require a powerful high voltage source. Corona-discharges result in a fast deterioration of the dielectric barrier. Also, corona-discharges erode working electrodes. The ozone generators need frequent maintenance by highly qualified personnel (for example, for replacement of dielectric barriers). The ozone generators consume a large amount of electrical power. The energy efficiency of implemented electro-synthesis processes is very low (1-2%). These generators need water cooling, and as a consequence, they require a source of water. This requirement makes them less sustainable. Excessive heat also plays a part in possible excessive nitrogen oxide production—especially in humid environments.
Irradiation of the liquids with an excimer lamp, more specially a dielectric barrier discharge excimer lamp filled with xenon or argon is one of effective techniques to disinfect the liquids and remove contaminants. However, the existing excimer lamps are inefficient due to their design limitations; the inventors or manufacturers of the lamps do not provide any criteria for the selection of the diameters, shape, and lengths of the emitting sleeves of the lamps; for changing the conductivity of the emitting sleeves; for choosing end sides of the lamp; and for choosing an electrode, its type, material, coating, etc. The existing excimer lamps do not use the liquid being treated as one or more electrodes. The exciting excimer lamps require a high ignition voltage. Also, the existing excimer lamps have a high cost, and there is a high level of production of defective lamps. The degree of disinfection or purification of contaminated liquids with the existing treatment systems with excimer lamps is inadequate if the liquid's transmittance of UV is low. The existing treatment systems with excimer lamps have an inadequate flow rate of the treatment in a scheme for one lamp in a reactor.
The existing methods of concurrent exposure of a liquid to UV radiation and oxidants provide better disinfection and purification of contaminated liquids; however, the existing methods are designed and implemented as two independent unit processes. Hence, they result in a high failure rate, large power consumption, and high operating costs.